1. Field of the Invention
The present invention relates generally to a core for a gliding board and, more particularly, to a core for a snowboard.
2. Description of the Art
Specially configured boards for gliding along a terrain are known, such as snowboards, snow skis, water skis, wake boards, surf boards and the like. For purposes of this patent, xe2x80x9cgliding boardxe2x80x9d will refer generally to any of the foregoing boards as well as to other board-type devices which allow a rider to traverse a surface. For ease of understanding, however, and without limiting the scope of the invention, the inventive core for a gliding board to which this patent is addressed is disclosed below particularly in connection with a core for a snowboard.
A snowboard includes a tip, a tail, and opposed heel and toe edges. The orientation of the edges depends upon whether the rider his her left foot forward (regular) or right foot forward (goofy). A width of the board typically tapers inwardly from both the tip and tail towards the central region of the board, facilitating turn initiation and exit, and edge grip. The snowboard is constructed from several components including a core, top and bottom reinforcing layers that sandwich the core, a top cosmetic layer and a bottom gliding surface that typically is formed from a sintered or extruded plastic. The reinforcing layers may overlap the edge of the core and, or alternatively, a sidewall may be provided to protect and seal the core from the environment. Metal edges (not shown) may wrap around a partial, or preferably a full, perimeter of the board, providing a hard gripping edge for board control on snow and ice. Damping material to reduce chatter and vibrations also may be incorporated into the board. The board may have a symmetric or asymmetric shape and may have either a flat base or, instead, be provided with a slight camber.
A core may be constructed of a foam material, but frequently is formed from a vertical or horizontal laminate of wood strips. Wood is an anisotropic material; that is, wood exhibits different mechanical properties in different directions. For example, the tensile strength, compressive strength and stiffness of wood have a maximum value when measured along the grain direction of the wood, while the mutually orthogonal directions perpendicular to the grain have a minimum value for these properties. In contrast, an isotropic material exhibits the same mechanical property regardless of its orientation.
Wood cores have traditionally been constructed with the grain 20 of all of the wood segments running either parallel to the base plane of the core (tip-to-tail), also known as xe2x80x9clong grainxe2x80x9d (FIGS. 1-2), perpendicular to the base plane, also known as xe2x80x9cend grainxe2x80x9d (FIGS. 3-4), or in a mixture of long grains and end grains where strips of the two types of grains are successively alternated. It also has been known to orient the long grain transversely across the core, in an edge-to-edge relationship. Consequently, in known wood cores, the segments have been oriented so that the grain extends in parallel to at least one of the orthogonal axes of the core. To date, however, the mechanical properties of the wood segments have been sufficient in both axial and off-axis directions to respond to the various directional forces applied to the board.
Snowboard manufacturers continually strive to produce a lighter board. It is known to reduce the weight of a board by employing lighter density materials in the core. As the density of wood decreases, however, mechanical properties may also decrease. A lower density wood segment that is oriented in standard fashion, with a long grain running tip-to-tail or edge-to-edge or an end grain extending perpendicular to the core, may be insufficient to withstand the loads commonly applied to a board during riding. Accordingly, there is a demand for an arrangement of a lightweight core for a gliding board that is capable of carrying various on and off-axis force induced stresses.
Dynamic loading conditions encountered during riding induce various bending and twisting forces on the board. The core and reinforcing layers are the structural backbone of the board, cooperating together to withstand these shear, compressive, tensile and torsional stresses. These force induced stresses may not be applied uniformly across the board but, rather, localized regions may be subject to a greater magnitude of a particular force. However, the core may not be specifically tuned to carry these localized loads.
For example, a rider usually lands a jump on the tail end, so it is that region of the board that typically encounters significant bending loads resulting in high longitudinal shear stresses. When a rider executes a hard turn on edge, the board typically is subjected to significant transverse bending loads resulting in high transverse shear stresses in the region between the edge and centerline of the board. Because bindings are mounted in an intermediate region of the board, significant compression strength may be required to withstand high compression loads applied by the rider to this region when landing a jump or during a hard turn on edge. Further, forces exerted on the bindings may create high point loads that can lead to pull out of the binding insert fasteners. The region of the board between the rider""s feet may encounter significant torsional loads due to opposing board twist along the board centerline when initiating or exiting a turn.
Accordingly, it would be advantageous to provide a core for a gliding board that is tuned to one or more specific, localized stresses or to a combination of such localized stresses.
The present invention is a flexible, durable, rider responsive core for a gliding board, such as a snowboard. The core imparts strength and stiffness so that a board incorporating the core may carry loads induced either in a direction parallel to an axis of the board as well as off-axis, or combinations thereof. The core cooperates with other components of the gliding board, such as with reinforcing layers positioned above and below the core, to provide a board with balanced torsion control and overall flexibility that quickly responds to rider induced loads, such as turn initiation and exit, that promptly recovers on landings after jumping or riding over bumpy terrain (moguls), and that maintains firm edge contact with the terrain. A gliding board incorporating the lightweight, resilient core rides fast and is easily maneuverable, and provides enhanced feel to the rider. A specific flex profile may be milled into the core, allowing a gliding board to be fine tuned to a specific range of riding performance.
The core includes a tip end, a tail end and opposed edges. Tip end refers to that portion of the core that is closest to the tip when the core is incorporated into the gliding board. Tail end, similarly, refers to that portion of the core that is closest to the tail when the core is assembled within the gliding board. The tip and tail ends may be constructed to extend the full length of the gliding board and be shaped to match the contour of the tip and tail of the gliding board. Alternatively, the core may extend only partially along the length of the gliding board and not include compatible end shapes. Symmetrical and asymmetrical core shapes are contemplated.
The core is formed from a thin, elongated member with a thickness that may vary, for example from a thicker central region to more slender ends, imparting a desired flex response to the board. However, a core of uniform thickness also is contemplated. Prior to incorporation into the gliding board, the core may be substantially flat, convex, or concave, and the shape of the core may be altered during fabrication of the gliding board. Consequently, a flat core may ultimately include a camber, and have upturned tail and tip ends, after the gliding board is completely assembled.
The gliding board preferably includes an anisotropic structure, such as wood, having a principal axis (the direction of the grain when the anisotropic structure is wood) along which a mechanical property that influences the riding performance of the gliding board has a maximum value. The principal axis may be defined by an angle relative to a plane formed by any two of the longitudinal axis, transverse axis and normal axis of the core. The anisotropic structure is oriented so that the principal axis is not in alignment with, or is not parallel to, any of these core axes. Although the anisotropic structure may be arranged to provide a maximum value for a particular contemplated load, preferably the principal axis is oriented to provide a balanced value for two or more anticipated load conditions. In the latter case, the principal axis may be oriented so that it does not provide a maximum value for any of the contemplated loads but, rather, a desired blended value. Where the anisotropic structure is wood, the grain direction of the wood does not extend in a direction that is parallel with any of the three axes. In such an off-axis orientation, the wood in the core is not oriented in long grain or end grain fashion. This off-axis orientation is particularly suited for lower density anisotropic structures. The core may be formed partially or completely of off-axis anisotropic structures. Although a wood anisotropic structure is preferred, other anisotropic structures are contemplated including a fiberglass/resin matrix, a molded thermoplastic structure, honeycomb, and the like. Furthermore, one or more isotropic materials may be formed into an anisotropic structure that is suitable for use in the present core, for example glass, which itself is isotropic, may be formed into fibers that may be aligned with each other in a resin matrix to form an anisotropic structure.
In one embodiment of the invention, the core includes a thin, elongated member having a tip end, a tail end and a pair of opposed edges. The core includes a longitudinal axis extending in a tip-to-tail direction, a transverse axis extending in an edge-to-edge direction and a normal axis. The thin, elongated member includes an anisotropic structure that has a principal axis along which a mechanical property has a maximum value, where the mechanical property is selected from one or more of compressive strength, compressive stiffness, compressive fatigue strength, compressive creep strength, tensile strength, tensile stiffness, tensile fatigue strength and tensile creep strength. The anisotropic structure is arranged in the core member so that the principal axis is not aligned with, or is not in parallel to, each of the longitudinal, transverse and normal axes of the core member. In one arrangement, the principal axis has an angle of approximately 45xc2x0 relative to one of the axes of the core member. Two or more off-axis anisotropic structures may be employed in the core and, preferably, they are arranged side-by-side with the respective principal axes extending in opposite relative directions. Alternatively, a single off-axis anisotropic structure may be employed alone or in conjunction with one or more anisotropic structures that are oriented so that their respective principal axes are aligned with or parallel to the axes of the core. The one or more non-parallel or unaligned anisotropic structures may be provided throughout the core or only in selected portions of the core. The direction of the anisotropic structures in the varying portions of the core may have different orientations as compared to one another.
In another embodiment of the invention, a thin, elongated core member includes a vertical lamination of thin strips of one or more anisotropic structures, preferably extending in a tip-to-tail direction. The principal axis of at least one of the anisotropic structures extends off axis relative to the axes of the core. Two or more different strips of anisotropic structures may be arranged in an alternating pattern and, preferably, the principal axis of the two anisotropic structures extend in opposite relative directions. In a preferred embodiment, the anisotropic structure is wood and the principal axis lies along the grain of the wood. In this arrangement, the principal axis of a first anisotropic structure may be oriented at approximately 45xc2x0 from the base plane toward the tip end (+45xc2x0) and the principal axis of an adjacent second anisotropic structure may be arranged at 45xc2x0 from the base plane toward the tail end (xe2x88x9245xc2x0). Other angles of the principal axis are contemplated, and the different anisotropic structures may be formed from the same or from a different density wood.
In another embodiment of the invention, a thin, elongated core member includes at least three different anisotropic structures, each having a principal axis oriented in a direction relative to the axes of the core that differs from the others. One or more of the three different anisotropic structures may have a principal axis that is off-axis relative to the orthogonal axes of the core.
In another embodiment of the invention, a thin, elongated core member includes selected regions that may be longitudinally spaced from each other. Each spaced region includes an anisotropic structure that has a principal axis oriented in a direction that differs from the other regions, providing the core with different mechanical properties at the spaced regions.
A still further embodiment of the invention includes a gliding board incorporating a thin, elongated core as described in any of the embodiments herein. The gliding board may further include a reinforcing layer, such as one or more sheets of a fiber reinforced matrix, above and below the core. A bottom gliding surface and a top riding surface also may be provided, as may perimeter edges for securely engaging the terrain. Damping and vibrational resistant materials also may be included, as appropriate.
It is an object of the present invention to provide a lightweight core for a gliding board.
It is another object of the present invention to provide a core for a gliding board with the structural integrity to handle the anticipated mechanical loads placed on the gliding board, particularly those forces that are applied off-axis to the board.
It is a further object of the invention to provide a core for a gliding board having selected regions of varying mechanical properties that are specifically tuned to the particular loads that will be applied to that region of the core.
Other objects and features of the present invention will become apparent from the following detailed description when taken in connection with the accompanying drawings. It is to be understood that the drawings are designed for the purpose of illustration only and are not intended as a definition of the limits of the invention.